MALMO, SWEDEN – Human papillomavirus (HPV) vaccination in Finnish girls aged 11-15 years was not associated with significantly higher risk of any of 38 potential adverse outcomes in a nationwide, retrospective cohort study.

Bruce Jancin/MDedge News

Dr. Jozica Skufca

“Anxiety and fear regarding adverse events are still very much alive and are associated with lack of acceptance of HPV vaccination,” Jozica Skufca, DVM, MIPH, observed while presenting the study findings at the annual meeting of the European Society for Paediatric Infectious Diseases.

“These results contribute valid evidence to combat public skepticism, anxiety, fears of adverse events, and possible opposition to HPV vaccination and consequently can contribute to increase HPV vaccination coverage in Finland as well as elsewhere,” added Dr. Skufca, who conducted this research while at the Finnish National Institute for Health and Welfare but is now an epidemiologist at P95, a privately held epidemiology and pharmacovigilance consulting firm in Heverlee, Belgium.

Finland introduced the bivalent HPV vaccine known as Cervarix, which is directed against HPV types 16 and 18, into the nation’s vaccination program in November 2013. The target population were girls aged 11-13 years, with catch-up vaccination at ages 14-15 years until 2015.

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Dr. Skufca utilized Finland’s comprehensive system of national health care registries to conduct a study of all 240,605 Finnish girls aged 11-15 years who were eligible for the bivalent HPV vaccine from November 2013 to December 2016. Only 56% of the target population, or 134,615 girls, were actually vaccinated. All were subsequently followed for more than a year.

HPV vaccination rates varied considerably between hospital districts, so the results were adjusted for that potential confounder. Risks also were adjusted for the number of hospital visits 1-2 years prior to vaccination, because healthier girls – those with fewer hospital visits – turned out to be more likely to get vaccinated.

The study’s main result was that HPV vaccination wasn’t associated with a significantly higher risk of any of the 38 adverse outcomes. To the contrary, vaccination was associated with significantly reduced risk of several of them: The risk of chronic fatigue syndrome was reduced by 25%, epilepsy and recurrent seizures were reduced by 28%, the risk of Henoch-Schönlein purpura was an adjusted 52% lower in children vaccinated against HPV, and the risk of malaise and fatigue was reduced by 24%.

Dr. Skufca drew particular attention to the 400% increased risk of Guillain-Barré syndrome in vaccinated children. While this may look impressive, it wasn’t a statistically significant difference. Guillain-Barré was a rare event, with only six cases occurring during 186,934 person-years of follow-up of vaccinated individuals and a single case in unvaccinated girls. Two cases occurred within 180 days after vaccination, for an adjusted 200% increase in risk, which was nonsignificant.